1. Field of the Invention
The invention relates to a manual lever drive for adjusting devices on seats, in particular, motor vehicle seats, for converting a lifting movement into a discontinuous rotation movement by employing a step-by-step mechanism.
2. Description of the Related Art
In today""s vehicles, self-locking gears or ratchet gears are used for adjusting different positions, such as, for example, the slant adjustment of the back rest, the seat height adjustment or the adjustment of the seat surface slant. Self-locking gears or ratchet gears, for example, in the form of simple planetary gears, are able, when configured accordingly, to receive loads occurring possibly in an accident situation, independent of whether at the moment of the accident an adjustment process was carried out or not. In many cases, the adjustment in the end is carried out by a rotational movement which however cannot be easily and comfortably performed because of lack of space. As an example, the problem in regard to operating the rotary adjuster for the back rest is mentioned in this context which is to be adjusted by an actuator hand wheel which is often arranged so closely to the inner parts of the car body that an ergonomic operation cannot be realized.
Step-by-step mechanisms for converting two-way alternating lifting movements into a discontinuous rotational movement are used already in many variations in the field of motor vehicle seats; frequently, ratchet gears and free wheel brake roller configurations are used. In order to realize an ergonomic operation, in many cases rotatory step-up or step-down gears are used after conversion of the lifting movement into the rotational movement in order to bring the forces and adjusting parameters into the required ratio relative to one another. A plurality of these employed mechanisms require for a correct function internal control paths for their activation; for example, in the case of ratchet gears a pawl must first be brought into engagement before the movement can be finally transmitted. Accordingly, of the entire movement to be provided by the operator only a minimal portion can be utilized for the actual adjustment so that the xe2x80x9ctotal mechanical efficiencyxe2x80x9d decreases.
It is an object of the present invention to provide a manual lever drive for adjusting devices which eliminates the aforementioned disadvantages of known systems and with which particularly the initial rotational angle relative to the lifting angle introduced by the manual lever is enlarged.
In accordance with the present invention, this is achieved in that the output member of the step-by-step mechanism is coupled with a rotating adjusting member of the adjusting device while the input member of the step-by-step mechanism is connected to the transmission member actuated by the manual lever for torque transmission, wherein the manual lever is pivotably supported on a support arm and pivotable about a first axis of rotation and its respective pivot angle imparts to the transmission member, arranged on a second axis of rotation, a pivot movement enlarging the corresponding rotational angle of the second axis of rotation on which the input member of the step-by-step mechanism is arranged.
For the transmission of the travel stroke or of the rotational angle, a lever drive, which can be referred to as a kinetic transmission, is connected upstream of the conversion of the lifting movement into a rotational movement; this provides, on the one hand, a very simple inexpensive realization and, on the other hand, with a corresponding selection of the transmission ratio, the control path required in the downstream system is also transmitted so that with regard to the actual actuation element the ratio of effective path to empty run is improved. In this connection, the actuation of such a lever drive can be configured, even for minimal space availability, in a comfortable way. Important in connection with the present solution are the two axes of rotation wherein on the first axis of rotation the manual lever is supported while the second axis of rotation represents the input member for the step-by-step mechanism, wherein the transmission member is fixedly connected with the input member forming the second axis of rotation, wherein the transmission member, in turn, can be actuated by the manual lever. As a result of the spacing of the axes of rotation from one another and as a result of the spacing of the second axis of rotation to the contact point of the manual lever on the transmission member, upon deflection of the manual lever by a certain angle a substantially greater angle results at the transmission member; consequently, a greater rotational angle on the second axis of rotation driving the step-by-step mechanism is realized. This reduces the empty run of the system which can be felt by the operator, the empty run being reduced according to the ratio of the aforementioned spacings.
In a first embodiment of the invention, the transmission member is a pivot lever fixedly connected to the input member which, by means of followers engaging opposed sides of the load arm of the manual lever, can be pivoted via the manual lever in one or the other rotational direction. In this connection, the followers of the pivot lever are advantageously pins projecting from the pivot lever and contacting control cutouts on the load arm of the manual lever.
In order to return the pivot lever after each switching step and thus also the manual lever into the initial position, the pivot lever has a return arm which is loaded by a stationary spring member and can thus be returned from any rotational position into a zero position. In this connection, the spring member can be in the form of a spiral spring secured on the housing of the step-by-step mechanism which engages with radially projecting spring fingers opposed sides of the return arm of the pivot lever.
Conventionally, the person adjusting the vehicle seat is seated on the seat and exerts, because of the person""s weight, a load on the adjusting element against which the position is to be adjusted with fine adjusting steps. For this purpose, a correspondingly great actuation force is to be applied which, however, to the seat occupant appears to be normal and is thus acceptable. However, when the seat is to be adjusted from the outside, i.e., when the operator is stands next to the vehicle, it is desirable to obtain a quick adjustment of the seat with a few pumping movements. These two aforementioned typical different operating states require for a consequent realization also different transmission ratios. A high transmission ratio of, for example, 1:4 in the case of the unloaded seat to be quickly adjusted is desirable while, when the seat is loaded, a minimal transmission ratio is desired for a precise and fine adjustment. For realizing these possibilities, according to a further embodiment of the invention, the pivot lever, which is provided as the transmission member, is formed by a spring saddle and a lever bracket connected thereto which receives in a contacting way between its two spaced-apart spring legs an end portion of the load arm of the manual lever which end portion is provided with curved control surfaces. In this connection, the leaf-spring-like spring legs are fixedly correlated with the pivot lever wherein the contact between the control surfaces on the load arm of the manual lever and the spring legs of the pivot lever is closer to the second axis of rotation than the contact point between the control surfaces and the spring legs for a somewhat pivoted load arm of the manual lever. In this connection, in the case of a great counter load on the pivot lever, the loaded spring leg experiences such a load that bending of the spring about the clamping location occurs and, in cooperation with the correspondingly curved control surfaces on the end portion of the load arm of the manual lever, the spring leg experiences a displacement of the contact point away from the second axis of rotation to the rear. This causes an automatic change of the transmission ratio. The transmission changes load-dependently by using the aforementioned spring legs, which are mentioned only as an example and which form elastic elements within the transmission chain. Accordingly, for such an arrangement first the empty run angle of the step-by-step mechanism arranged downstream is passed quickly with minimal load and thus high transmission while the subsequent loading of the seat adjusting element leads to a continuous reduction of the transmission and thus an ergonomic operation.
A further transmission, which is adjustable automatically as a function of the load but in steps, is provided by a spring saddle secured on the lever bracket of the pivot lever which has a U-shaped support body having on the lateral legs engaging the load arm of the manual lever a multi-step spring bracket, respectively, between which the load arm of the manual lever with its contact sections engages continuously during its pivot movement. In this connection, each spring bracket can have, for example, three spaced-apart, successively arranged bracket sections which successively become narrower and engage the clamping projections on the load arm of the manual lever with increasing clamping force. Thus, three load stages are provided wherein the individual bracket sections are configured such that the force required for pressing apart the clamping sections increases with increasing spacing of the corresponding clamping section from the second axis of rotation. For smaller output moments, the force is transmitted via the bracket section closest to the axis of rotation so that for small loads a great transmission is realized. The force which can be transmitted at this location is limited by the opening force of the clamping section. When the output load increases to a level above the transmittable force on the first bracket section, the force is transmitted by the second bracket section which is farther removed from the axis of rotation. Accordingly, the transmission ratio at this location is smaller than before. The aforementioned statements apply analogously to the exemplary third contact location of the corresponding bracket section.
Instead of a transmission ratio which changes automatically upon actuation of the manual lever, it would also be possible to provide a device with which the transmission ratio is controlled in a targeted way. This could be realized, for example, in that on the manual lever a pushbutton is arranged which, by means of a sliding linkage, is connected to a connecting link bracket which is movable relative to the load arm of the manual lever as well as with regard to the bracket lever; by means of the connecting link bracket, when the user actuates the pushbutton, a constructively fixed transmission is activated in order to achieve, for example, a quick adjustment at a high transmission ratio.
The afore described embodiments of a transmission mechanism are arranged upstream of a step-by-step mechanism. Instead, an embodiment of a lever drive can be provided wherein the step-by-step mechanism is integrated in a special embodiment. For this purpose, according to an advantageous embodiment of the invention, the transmission member is comprised of a spool body fixedly connected on the shaft of the second axis of rotation and a wrap spring surrounding it. The wrap spring has spring ends formed as elastic follower arms between which a curved head of a load arm of the manual lever is received. In this connection, the follower arms of the wrap spring advantageously are loaded by one spring member, respectively, in the direction of a zero position, respectively. The elastic follower arms of the wrap spring serve however not only for controlling the coupling function but, at the same time, are formed as contact surfaces for the curved head on the load arm of the manual lever. These contact surfaces bend load-dependently and enable thus a high functional integration. For a pivot movement of the load arm of the manual lever in one direction, the wrap spring is closed for this movement direction and the spool body, for an initially high transmission, is entrained wherein the transmission ratio as a result of gliding of the curved head on the corresponding follower arm is adjusted automatically to the load. Upon pivoting of the load arm of the manual lever into the initial position, the previously driven follower arm is loaded by the restoring spring member such that the wrap spring is opened and the spool body is no longer driven but instead, as a result of friction in the downstream adjusting element of the seat, remains in this position. Since for a corresponding pivot movement of the load arm of the manual lever in the opposite direction, the aforementioned effect happens also, but in the opposite direction, a step-by-step mechanism acting in both directions is realized with integrated automatic load-dependent transmission.
A further embodiment of a step-by-step mechanism integrated with the lever drive can be preferably obtained in that the transmission member is formed by a drum-shaped cup fixedly connected to the shaft of the second axis of rotation and a wrap spring arranged therein. The wrap spring has spring ends in the form of follower arms radially projecting toward the drum-shaped cup center which are received in the receiving space of a pawl arranged on the load arm of the manual lever. Since depending on the configuration of the seat adjusting element, the inner friction is possibly reduced in comparison to the friction upon return of the wrap spring, it may be advantageous to employ two wrap springs acting in opposite directions, respectively, the configuration being identical in other respects, so that restoring springs can be eliminated, if needed.